全文获取类型
收费全文 | 5278篇 |
免费 | 330篇 |
国内免费 | 45篇 |
专业分类
电工技术 | 118篇 |
综合类 | 51篇 |
化学工业 | 1275篇 |
金属工艺 | 159篇 |
机械仪表 | 150篇 |
建筑科学 | 263篇 |
矿业工程 | 33篇 |
能源动力 | 350篇 |
轻工业 | 774篇 |
水利工程 | 43篇 |
石油天然气 | 79篇 |
武器工业 | 12篇 |
无线电 | 223篇 |
一般工业技术 | 803篇 |
冶金工业 | 509篇 |
原子能技术 | 48篇 |
自动化技术 | 763篇 |
出版年
2024年 | 12篇 |
2023年 | 43篇 |
2022年 | 92篇 |
2021年 | 193篇 |
2020年 | 136篇 |
2019年 | 151篇 |
2018年 | 209篇 |
2017年 | 223篇 |
2016年 | 222篇 |
2015年 | 191篇 |
2014年 | 248篇 |
2013年 | 515篇 |
2012年 | 286篇 |
2011年 | 351篇 |
2010年 | 314篇 |
2009年 | 256篇 |
2008年 | 246篇 |
2007年 | 226篇 |
2006年 | 157篇 |
2005年 | 104篇 |
2004年 | 138篇 |
2003年 | 138篇 |
2002年 | 162篇 |
2001年 | 97篇 |
2000年 | 83篇 |
1999年 | 70篇 |
1998年 | 146篇 |
1997年 | 101篇 |
1996年 | 55篇 |
1995年 | 47篇 |
1994年 | 61篇 |
1993年 | 46篇 |
1992年 | 26篇 |
1991年 | 16篇 |
1990年 | 21篇 |
1989年 | 19篇 |
1988年 | 17篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 26篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 20篇 |
1981年 | 20篇 |
1980年 | 15篇 |
1978年 | 6篇 |
1977年 | 12篇 |
1976年 | 23篇 |
1975年 | 9篇 |
1974年 | 11篇 |
排序方式: 共有5653条查询结果,搜索用时 171 毫秒
61.
The effects of aging time of Cr(III) solutions on the structural, thermal, magnetic, and morphological properties of chromium polyacrylate complexes were studied. Chromium retention was found to increase with longer aging periods. IR spectra revealed the formation of polychelate structures with noticeable changes on aging. The interaction of multivalent, polynuclear Cr(III) species with the polymer backbone resulted in a decrease in thermal stability for the complexes prepared from olated chromium solutions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 490–493, 2005 相似文献
62.
63.
Alper Sarıoğlan Ömer Tunç Savaşçı Ayşe Erdem-Şenatalar Vu Thu Ha Gilbert Sapaly Younès Ben Taârit 《Catalysis Letters》2007,118(1-2):123-128
MFI type inorganic carrier was used in two different cationic forms, hydrogen and calcium respectively. MFI-supported molybdenum
and rhenium catalysts were prepared. The activities of the catalysts were compared for the aromatization reaction of methane.
Higher activity values were attained with the catalysts supported on HZSM-5. Aromatics were also observed with the catalysts
supported on CaZSM-5, despite their deficiency in acid sites. Highly dispersed rhenium is expected to be formed with the use
of the inorganic carrier in calcium form. On the other hand, lower reaction rates were observed with rhenium supported on
CaZSM-5, in spite of the improved dispersion of the active rhenium species on this catalyst. This was interpreted in terms
of the critical role of the acid sites in the conversion of methane to aromatics, compared to the improved dispersion of the
active metal. 相似文献
64.
65.
Antonio Di Nola Ioana Leuştean 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2014,18(12):2349-2363
We initiate a deep study of Riesz MV-algebras which are MV-algebras endowed with a scalar multiplication with scalars from \([0,1]\) . Extending Mundici’s equivalence between MV-algebras and \(\ell \) -groups, we prove that Riesz MV-algebras are categorically equivalent to unit intervals in Riesz spaces with strong unit. Moreover, the subclass of norm-complete Riesz MV-algebras is equivalent to the class of commutative unital C \(^*\) -algebras. The propositional calculus \({\mathbb R}{\mathcal L}\) that has Riesz MV-algebras as models is a conservative extension of ?ukasiewicz \(\infty \) -valued propositional calculus and is complete with respect to evaluations in the standard model \([0,1]\) . We prove a normal form theorem for this logic, extending McNaughton theorem for ? ukasiewicz logic. We define the notions of quasi-linear combination and quasi-linear span for formulas in \({\mathbb R}{\mathcal L},\) and relate them with the analogue of de Finetti’s coherence criterion for \({\mathbb R}{\mathcal L}\) . 相似文献
66.
Olivier Renoult Jean-Pierre Boilot Frédéric Chaput Renée Papiernik Liliane G. Hubert-Pfalzgraf Martine Lejeune 《Journal of the American Ceramic Society》1992,75(12):3337-3340
The sol–gel method has been developed for the preparation of pure Ba(Mg1/3 Ta2/3 )O3 ceramics. This involves the reaction of the heterometallic alkoxide Ta2 Mg(OEt)12 with hydrated barium hydroxide Ba(OH)2 ·8H2 O. Complete crystallization of the sol–gel-derived powder is achieved at 600°C, leading to a cubic perovskite type phase. After sintering at 1400°C (2–5 h), a trigonal cell arises from Mg–Ta ordering (the degree of order is greater than 0.9), and about 98.5% of the theoretical density is obtained. Preliminary microwave dielectric measurements show that the dielectric constant and the unloaded Q u of the ceramics are 24.2 and 6750, respectively, at 7.7 GHz. 相似文献
67.
68.
69.
Jose Brisson 《Polymer Engineering and Science》2004,44(2):241-251
A review of past and present studies on orientation, rheology, and FTIR investigations on a hydrogen bond–forming polymer, poly(vinyl phenol) (PVPh), and its blends with polyethylene oxide (PEO), poly(methyl methacrylate) (PMMA), and poly(vinyl methyl ether) (PVME) is presented. Orientation is analyzed on the basis of deformation‐induced orientation and relaxation. For deformation, it is proposed from recent molecular modeling studies that orientation is similar for flexible backbone polymers of the types studied. To investigate relaxation, dynamical rheology analysis was performed previously on PVPh/PEO blends and global molecular weight between entanglement, Me, and chain friction ζ were estimated. Me remained close to that of the polymer forming the dominant network, a discontinuity being observed near 50 mole percent. Friction coefficient exhibited a maximum near that of the orientation function of this system. Near‐infrared measurements also showed a maximum in the number of interchain hydrogen bonds at this concentration, although broader than that of orientation or of the friction coefficient. For strongly interacting blends, it is proposed that a break in orientation behavior would be associated with the dominant network present, and therefore to Me, whereas ζ will dictate whether orientation decreases or increases in a given network domain. 相似文献
70.
Christine Baatz Nadine Thielecke Ulf Prüße 《Applied catalysis. B, Environmental》2007,70(1-4):653-660
In this work, two deposition–precipitation methods for the preparation of gold catalysts for glucose oxidation were investigated. Thus far, gold colloids immobilized on carbon have been used for catalytic glucose oxidation, but the long-term stability of these systems was not sufficient. To improve the long-term stability we used the deposition–precipitation methods using NaOH (DP NaOH) or urea (DP urea) as precipitation agents as they were described by Haruta and Dekkers, respectively, using alumina as a support material. With these methods, it was possible to prepare highly active and selective catalysts which showed an excellent long-term stability. DP urea was found to be the preferred method, because in contrast to DP NaOH, no losses of gold occurred during the preparation, and it was possible to adjust various gold contents up to 10 wt% Au. 相似文献